proguard: Add rules for retrofit2

app/proguard-rules.txt

@@ -23,4 +23,19 @@
 -dontwarn org.apache.http.**
 -dontwarn android.net.http.AndroidHttpClient
 -dontwarn com.google.android.gms.**
--dontwarn com.android.volley.toolbox.**
+-dontwarn com.android.volley.toolbox.**
+
+
+# See https://square.github.io/retrofit/
+# Platform calls Class.forName on types which do not exist on Android to determine platform.
+-dontnote retrofit2.Platform
+# Platform used when running on Java 8 VMs. Will not be used at runtime.
+-dontwarn retrofit2.Platform$Java8
+# Retain generic type information for use by reflection by converters and adapters.
+-keepattributes Signature
+# Retain declared checked exceptions for use by a Proxy instance.
+-keepattributes Exceptions
+
+
+# See https://github.com/square/okio#proguard
+-dontwarn okio.**